1. Field of the Invention
The present invention relates to a display controller contained in a microcomputer and including a display driver, and more specifically to a transfer of display data from a display memory to a display segment signal output terminals in such a display controller.
2. Description of Related Art
In conventional display controllers for fluorescent character display tubes and/or liquid crystal displays, a count clock is counted by a timing counter, and a count value of the timing counter is supplied to an address generator, which supplies a display memory with an address for display data of a character to be displayed next. Thus, display data of a character is read out from the display memory and supplied to a display data latch in parallel. In the case of the fluorescent character display tube, the display data latch outputs the latched display data through an output buffer to display segment signal output terminals, which are connected to a fluorescent character display tube. In addition, the count value of the timing counter is also supplied to a display timing decoder, which has an output connected through another output buffer to display digit signal output terminals, which are also connected to the fluorescent character display tube. In the case of the liquid crystal display (LCD), the display data latch outputs the latched display data through a segment driver to display segment signal output terminals, which are connected to the LCD display. In addition, the count value of the timing counter is also supplied to a common driver having an output connected to common driver output terminals, which are also connected to the LCD display.
As mentioned above, the conventional display controller is such that the display data is transferred from the display memory to the display data latch in parallel. Therefore, the number of wiring lines extending from the display memory to the display data latch has to be the same as the number of the display segment output terminals. Namely, the number of wiring lines for transferring the display data from the display memory to the display data latch in parallel is increased with the number of the display segments. As a result, the chip area of a microcomputer including the display controller inevitably increases. Further, in the arrangement of the inside of the microcomputer, there occurs a restriction that the display memory and the display segment output terminals should be disposed in the neighborhood to each other.